For a study on whether everything we eat is associated with cancer, academics randomly selected 50 ingredients from recipes in The Boston Cooking-School Cook Book. Most foods had studies behind them claiming both positive and negative results.

So according to the studies pretty much everything we eat both causes and protects against cancer!

Heard somewhere regarding why there are so many conflicting studies about whether this food or that food is good or bad for you, that about the only way you could definitely settle any nutrition myths would be if you took two groups of people (accounting for race/gender factors), locked them both in climate-controlled rooms, and monitored both groups, with one being the control and the other being given the specific food or nutrition in question, until they died. But that's pretty much impossible so that's why one week you'll hear about this food being good for you, while next week, they'll be another study saying that it's bad for you.

But that's pretty much impossible so that's why one week you'll hear about this food being good for you, while next week, they'll be another study saying that it's bad for you.

Also I guess that many types of food can be both good and bad for you at the exact same time but in different ways, and might even be helpful in preventing certain types of cancer but put you at a higher risk of other types of cancer.

It might well also be affected by which other foods you did or didn't eat; as well as by the genetics of the particular people in question; as well as by the form of the food (they keep saying "red meat". do you mean fresh meat or nitrate-cured sausage? and what had the animal who produced it been eating?); as well as the actual nutrient content of the food (there are thousands of varieties of, say, beans, and probably thousands of different soils they could be grown on, with large numbers of possible amendments; even time of day of harvest can affect nutrient content.)

It's a chronic problem, and not only in this area. If you include all the variables, the situation is too complicated to find anything out. But if you limit the variables, whatever you've found out may be wrong in actual practice, because what you left out may be important.

It is, nevertheless, often possible (not to mention necessary, if we're to function at all) to come to at least tentative conclusions. But it's important to remember that they're tentative. Which makes for good science; but not for good headlines.